1. Field of the Invention
The present invention relates to a cooling system for an automotive internal combustion engine, which includes a cylinder head water jacket and a cylinder block water jacket made independent of each other, and a head-side cooling system and a block-side cooling system connected with a common radiator.
2. Description of the Prior Art
In the prior art, there has been proposed a cooling system for an internal combustion engine, in which the water jackets of a cylinder head and a cylinder block are made independent of each other to provide head-side and block-side cooling lines connected to a common radiator and a common water pump, as is disclosed in Japanese Patent Laid-Open No. 213918/1984. In this cooling system, a water pump has its discharge pipe branched to head-side and block-side conduits connected to the respective inlets of the head-side and block-side water jackets. Moreover, the head-side and block-side passages are variably throttled to control the water flow rates and accordingly the water temperatures.
In the aforementioned cooling system of the prior art, the discharge pipe of the water pump is shared between the head and block sides so that the water jackets of the two sides have substantially the same inlet water temperature. The smaller difference between the inlet and outlet temperatures of the jackets is the more advantageous for the anti-knocking performance of the engine. Since the aforementioned system of the prior art has the common inlet water temperature, however, the flow rate has to be throttled at a higher temperature side if the (average) water temperature is differentiated according to the difference in the flow rate, thus raising a problem that the difference between the inlet and outlet temperatures of the jackets is enlarged.